Variable pitch propeller systems incorporate various safety devices to ensure safe operation in case of a hydraulic failure. One type of safety device is a propeller blade counterweight. The propeller blades are arranged on the propeller hub, and the counterweight is attached to the base of the blade and produces a twisting moment on the blade when the propeller is rotating such that the net twisting moment on the blade, including the total blade mass and aerodynamic twisting forces, is in the increase-pitch direction. The net twisting moment can reduce over-speed and high drag conditions if the hydraulic operation of pitch change system fails.
Conventional counterweights are typically optimized to reduce weight by placing the counterweight at the largest radius from the blade rotational axis allowed by the hub envelope supporting the blade. Since the blade counterweight is rigidly attached to the blade, the counterweight must rotate from full reverse to the feather position. In order for the blade to transition to the feather position, the counterweight must pass by an adjacent blade. As the number of blades formed on the propeller hub increases, the distance between adjacent hub arms decreases such that the counterweight contacts an adjacent blade when transitioning to a feather position. Consequently, the overall length of the conventional counterweight must be reduced as the number of propeller blades increase, thereby causing the propeller weight to increase.